ORGANIC
LETTERS
2003
Vol. 5, No. 24
4717-4720
Automated Synthesis of a Protected
N-Linked Glycoprotein Core
Pentasaccharide
,†
Daniel M. Ratner, Erika R. Swanson, and Peter H. Seeberger*
Department of Chemistry, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139
Received September 27, 2003
ABSTRACT
Described is the first automated solid-phase synthesis of the core N-linked pentasaccharide, common to all N-linked glycoproteins via stepwise
assembly from mono- and disaccharide building blocks. The challenging â-mannosidic linkage was incorporated by the inclusion of a disaccharide
trichloroacetimidate. This automated synthesis provides rapid access to an oligosaccharide common to an entire class of glycoconjugates.
Co-translational modification of proteins by glycosylation
of asparagine residues includes three classes of N-linked
oligosaccharides: high-mannose, hybrid, and complex-type
mannans.1 In addition to the many functions of these
branched glycans in mammalian cells, they are found on the
glycoproteins of a variety of pathogens, including the viral
envelope of HIV,2 Ebola,3 and some coronaviruses.4 Rapid
and reliable access to these branched glycans by automated
synthesis would facilitate further investigation into the
biological role of these glycoconjugates and their potential
application as carbohydrate-based vaccines.5 Currently,
synthetic N-glycans are used to study carbohydrate/protein
interactions using isothermal calorimetry,6 carbohydrate
arrays,7 and the structural analysis of such complexes (X-
ray, NMR).8
target of several recent syntheses in solution9 and on solid
support.10 This pentasaccharide contains a number of syn-
thetic challenges, including branching, â-(1f4) glucosamine
linkages, and most notably, the daunting â-mannoside.
Described is the first automated solid-phase synthesis of
the N-linked core pentasaccharide 1. Retrosynthetic analysis
of 1 revealed that the target could be accessed using just
three distinct building blocks, two monosaccharides 2, 3,11
and one disaccharide 4 (Figure 2). To avoid anomeric
mixtures on the solid support, the â-mannosidic linkage was
(5) Calarese, D. A.; Scanlan, C. N.; Zwick, M. B.; Deechongkit, S.;
Mimura, Y.; Kunert, R.; Zhu, P.; Wormald, M. R.; Stanfield, R. L.; Roux,
K. H.; Kelly, J. W.; Rudd, P. M.; Dwek, R. A.; Katinger, H.; Burton, D.
R.; Wilson, I. A. Science 2003, 300, 2065.
(6) Shenoy, S. R.; Barrientos, L. G.; Ratner, D. M.; O’Keefe, B. R.;
Seeberger, P. H.; Gronenborn, A. M.; Boyd, M. R. Chem. Biol. 2002, 9,
1109.
(7) Adams, E. W.; Uberfeld, J.; Ratner, D. M.; O’Keefe, B. R.; Walt,
D, R.; Seeberger, P. H. Angew. Chem., Int. Ed. 2003, 42, in press.
(8) Barrientos, L. G.; Louis, J. M.; Ratner, D. M.; Seeberger, P. H.;
Gronenborn, A. M. J. Mol. Biol. 2003, 325, 211. Botos, I.; O’Keefe, B. R.;
Shenoy S. R.; Cartner, L. K.; Ratner, D. M.; Seeberger, P. H.; Boyd, M.
R.; Wlodawer, A. J. Biol. Chem. 2002, 277, 34336.
The three major classes of N-linked glycans contain a
common core pentasaccharide (Figure 1) that has been a
† Current Address: Laboratorium fu¨r Organische Chemie, ETH
Ho¨nggerberg, Zurich, Switzerland.
(1) Dwek, R. A. Chem. ReV. 1996, 96, 683. Imperiali, B.; O’Connor, S.
E. Curr. Opin. Chem. Biol. 1999, 3, 643.
(2) Feizi, T. Glycobiology of AIDS. Carbohydrates in Chemistry and
Biology; Wiley-VCH: New York, 2000; Vol. 4, pp 851-863.
(3) Lin, G.; Simmons, G.; Pohlmann, S.; Baribaud, F.; Ni, H. P.; Leslie,
G. J.; Haggarty, B.; Bates, P.; Weissman, D.; Hoxie, J. A.; Doms, R. W. J.
Virol. 2003, 77, 1337.
(9) For a review of recent solution-phase syntheses of the core penta-
saccharide, see ref 18.
(10) Wu, X.; Grathwohl, M.; Schmidt, R. R. Angew. Chem., Int. Ed.
2002, 41, 4489.
(11) Mayer, T. G.; Kratzer, B.; Schmidt, R. R. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2177.
(4) Delmas, B.; Laude, H. Virus Res. 1991, 20, 107.
10.1021/ol035887t CCC: $25.00 © 2003 American Chemical Society
Published on Web 11/01/2003